Researchers have been investigating the possibility of 3D printing lunar regolith — without any other materials involved.
There is no 3D printing taking place on our Moon today, but this is very likely to change in coming years. With multiple programs attempting to place humans on that celestial body, there will be a need for structures. Rather than launching all the materials for the structures from Earth — which is quite expensive — the concept is to instead build from local materials.
The dominant local material on the Moon is called “regolith”. It’s the powder-like surface coating that was formed by millions of years of bombardment by meteors that repeatedly smashed boulders into dust. Unlike Earth soil, there are no organic components, hence the name “regolith” instead of “soil”.
There have been several studies looking into methods of 3D printing lunar regolith, and many of them involve using a binder. This is a common technique in today’s commercial 3D printing: binder jetting involves mixing a binder with a material powder.
That approach would certainly work, but it requires the cost of shipping the binder to the Moon from Earth. But what about using the regolith on its own with no binder?
That was the subject of a new research paper entitled, “Selective laser melting of partially amorphous regolith analog for ISRU lunar applications”. They investigated the possibilities of using the SLM 3D printing process using a regolith analog.
They used an analog regolith because, as you might guess, actual regolith is kind of hard to get these days. The researchers developed their own basalt-based regolith that had a median particle size of 0.08mm, matching samples taken by Apollo astronauts.
They used a Nikon SLM SLM125HL device for testing, which uses an argon atmosphere in the build chamber to eliminate oxygen contamination. In an actual lunar 3D printing scenario, the build chamber would be a vacuum — also clear of oxygen.
Their experiment involved tweaking a number of variables to identify the optimal configuration for 3D printing raw regolith, including substrate type, powder composition, and the temperatures involved.
Their results were impressive, identifying the 100% amorphous basalt powder with a one-hour post-printing step at 900°C for annealing as the best combination.
They found that the annealing process was able to improve the compressive strength by 2X, as well as improving the microstructure and reducing porosity.
While largely successful, they also found that the quality of the output varied significantly between batches, and that the mechanical properties were sensitive to sample preparation, especially with pre-existing micro-cracks.
This is a good first step, and it’s clear there is much research yet to be done to make this a viable technology for testing in an actual lunar scenario.
Via HAL
